Apparatus for cycloidal acceleration and deceleration with partial constant velocity

ABSTRACT

A reversible rotary indexing mechanism capable of generating large indexing angles including those exceeding one revolution. A constant velocity rotary input is connected to a rotary output by an eccentric accelerating-decelerating drive means which, by reason of a shifting mechanism, is selectively disengageable with the output at a maximum velocity, zero acceleration condition, while at the same time a constant velocity drive from the input is connected to the output. Conversely, the constant velocity drive is disconnected at the same time that the accelerating-decelerating drive means is reconnected to accomplish deceleration. An output lock is also provided and actuators including composite cams can be utilized to accomplish the action of the shifting mechanism. 
     In addition, the mechanism can be used with higher harmonic components to increase the design flexibility with greater inherent dwell capabilities and significantly longer constant velocity ranges.

FIELD OF INVENTION

Apparatus for machine drives to achieve cycloidal acceleration anddeceleration with partial constant velocity.

BACKGROUND OF INVENTION

In my existing U.S. Pat. Nos. 3,789,676; 3,857,292; and 4,075,911, itwas shown how cycloidal motions, with or without the addition of higherharmonic components, would be generated with simple gear or chain typemechanisms. A common characteristic of all the various mechanisms shownwas that the output stroke was equal to the pitch circumference of agear or sprocket. In the case of linear output systems, the linearoutput stroke was equal to the pitch circumference of the indexing gearor sprocket; in the case of rotary output systems, the output indexangle was equal to the angle subtended by an arc on the output gear orsprocket whose length was equal to the pitch circumference of theeccentric index gear or sprockets. While these systems have beenusefully employed in many applications, they are handicapped ingenerating long strokes by requiring indexing gears or sprockets whichbecome impractically large.

It is one object of the present invention to provide an indexing systemwhich is capable of generating an accelerated-decelerated index strokeduring multiple revolutions of the index gear; accordingly, aproportionally smaller gear can be employed.

In such a multiple revolution gear index system, the natural dwellbetween the index strokes will become smaller as related to the inputangle than is that same natural dwell for a single revolution indexsystem.

It is another object of this invention to provide an indexing system inwhich the dwell between index strokes can be significantly extended andthereby to provide ample time for stoppage or reversal of the drivingmotor.

In a conventional cycloidal indexing system, the peak velocity reachedat or near midstroke is approximately two times the average velocityduring the stroke.

It is another object of this invention to provide an indexing system inwhich the peak velocity reached during the stroke is significantly lessthan two times the average velocity reached during the stroke.

Other objects and features of the invention will be apparent in thefollowing description and claims in which the principles of theinvention are set forth together with details of the structure whichwill enable a machine builder to utilize the invention, all inconnection with the best modes presently contemplated for the practiceof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

DRAWINGS accompany the disclosure and the various views thereof may bebriefly described as follows:

FIG. 1, a schematic side view of an accelerating-decelerating mechanismas disclosed in my U.S. Pat. No. 3,789,676.

FIG. 2, a top view of the mechanism shown in FIG. 1.

FIGS. 3 to 6, schematic sequential position diagrams of the mechanismshown in FIG. 1.

FIG. 7, a displacement diagram for cycloidal motion, over one cycle.

FIG. 8, a velocity diagram for cycloidal motion, over one cycle.

FIG. 9, an acceleration diagram for cycloidal motion, over one cycle.

FIG. 10, a side view of the mechanism of FIG. 1 altered fordisengagement.

FIG. 11, a side view of an additional engageable mechanism to achieveconstant velocity in the mechanism of FIG. 1.

FIG. 12, an illustrative velocity diagram for the mechanism of FIG. 11.

FIG. 13, a second illustrative velocity diagram for the mechanism ofFIG. 11.

FIG. 14, a side view of an additional engageable mechanism to hold orlock the mechanism of FIG. 1.

FIG. 15, a side view of a system which combines the mechanisms of FIGS.1, 10, 11 and 14, and provides a single cam mechanism for the actuationsthereof.

FIG. 16, a section taken on line 16--16 of FIG. 15.

FIG. 17, a plan view of one embodiment of the mechanism of thisinvention.

FIG. 18, a transverse section of the mechanism taken on line 18--18 ofFIG. 17.

FIG. 19, a transverse section of the mechanism taken on line 19--19 ofFIG. 18.

FIG. 20, a transverse section of the mechanism taken on line 20--20 ofFIG. 17.

FIG. 21, a transverse section of the mechanism taken on line 21--21 ofFIG. 17.

FIG. 22, a transverse section of the mechanism taken on line 22--22 ofFIG. 17.

FIG. 23, a partial section of the mechanism taken on line 23--23 of FIG.22.

FIG. 24, a partial section of the mechanism taken on line 24--24 of FIG.22.

FIG. 25, a transverse section of the mechanism taken on line 25--25 ofFIG. 17.

FIG. 26, a partial transverse section of the mechanism taken on line26--26 of FIG. 25.

FIG. 27, a transverse section of the mechanism taken on line 27--27 ofFIG. 17.

FIG. 28, a transverse section of the mechanism taken on line 28--28 ofFIG. 17.

FIG. 29, a composite timing diagram of an illustrative cycle showingoutput velocity and the timeposition relationship of the variousengaging mechanisms.

FIG. 30, a transverse section of a second embodiment, analogous to FIG.19 showing means to incorporate a higher harmonic as disclosed in myU.S. Pat. No. 4,075,911.

FIGS. 1 and 2 are simplified schematic drawings of one embodiment of anapproximate cycloidal motion generating mechanism from my U.S. Pat. No.3,789,676. An input gear 2 is mounted on an input shaft 4 which isjournalled in a suitable housing or frame and driven by an appropriateexternal drive system. Also journalled on the input shaft 4 is atangential link 6 which oscillates thereon as will be described. Adriving gear 8 is mounted on a shaft 10 journalled in the outboard endof the link 6, and an intermediate gear 12, also journalled in the link6, is formed to mesh with the input gear 2 and driving gear 8. Aneccentric gear 14 is mounted on the shaft 10 with an eccentricityapproximately equal to its pitch radius. This eccentric gear 14 mesheswith an output gear 16 mounted on a shaft 18 also journalled in thehousing or frame. A radial link 20 is also journalled on the outputshaft 18 at its one end; at its other end, the radial link 20 isjournalled to a stub shaft 22 mounted concentrically on the eccentricgear 14. It is the purpose of this radial link 20 to keep the eccentricgear 14 in mesh with the output gear 16 as the eccentric gear 14 movesthrough its rotational and translational path.

When the mechanism is in the position shown in FIG. 1, it is in anatural dwell position, i.e., a small rotation of the input gear 2causes a corresponding rotation of the driving gear 8 and the eccentricgear 14. This rotation of the eccentric gear 14 is accompanied by acorresponding movement of the shaft 22 about the shaft 18, such that thegear 14 literally rolls about the output gear 16 which remainsstationary or in dwell.

A qualatative schematic representation of the motion of the output gear16 during a complete 360° rotation of the driving gear 8 and eccentricgear 14, at 90° intervals, is shown in FIGS. 3-6. An arbitrary radialmarker line has been added to the output gear 16 to show its positionchange at these intervals. FIG. 3 shows the position of all gears at thecenter of the dwell, which is the same configuration as shown in FIG. 1.Additionally, a second position is shown in which the driving gear 8 andeccentric gear 14 have been rotated 10° counterclockwise (as driven byintermediate gear 12 and input gear 2). The rolling action of the gear14 on the output gear 16 which remains substantially stationary duringthis 10° interval can therefore be visualized. In this second position,the components are redesignated by the callout suffix letter a.

As the gears 8 and 14 continue to rotate counterclockwise, the outputgear 16 is accelerated and moves in the clockwise direction. After 90°of this rotation of gears 14 and 8, the position shown in FIG. 4 isreached. At this point, the acceleration of gear 16 in the clockwisedirection has reached its approximate maximum, and the velocity of thegear 16 in the clockwise direction is approximately equal to its averagevelocity.

As the gears 8 and 14 continue, their rotation counterclockwise fromtheir position shown in FIG. 4, the output gear 16 continues toaccelerate, at a decreasing rate, in the clockwise direction. After anadditional 90° of rotation of gears 14 and 8, the positions shown inFIG. 5 is reached. At this point, the acceleration of the gear 16 hassubstantially returned to zero, and its velocity in the clockwisedirection has reached an approximate maximum which is double the averagevelocity.

As the gears 8 and 14 continue to rotate counterclockwise from theposition shown in FIG. 5, the output gear 16 continues to rotateclockwise but is decelerating. After an additional 90° of rotation ofgears 8 and 14, or a total of 270° from the start of the cycle, theposition shown in FIG. 6 is reached. At this point, the deceleration ofthe output gear 16 is at or near maximum, while the velocity of theoutput gear 16, still in the clockwise direction, has slowed down toapproximately its average velocity.

As the gears 8 and 14 continue to rotate counterclockwise from theposition shown in FIG. 6, the output gear 16 continues to rotateclockwise, but is still decelerating, though now at a decreasing rate.After an additional 90° of rotation of gears 8 and 14, or a total of360° from the start of the cycle, the position shown in FIG. 3 is againreached, with the output gear 16 having completed one revolution and isnow again in dwell.

It can be seen, therefore, that as the input gear 2 is driven by someexternal power means at a substantially constant angular velocity, thegears 8 and 14 are driven by the intermediate gear 12. Gears 8 and 14have an angular velocity which is determined by the superposition of theeffect of the oscillation of link 6 about shaft 4 on the velocitycreated by the input gear 2 so gears 8 and 14 do not rotate as aconstant angular velocity. And the oscillation of the gear 14 along thearcuate path controlled by radial link 20 and created by its eccentricmounted on shaft 10 creates another superposition on the velocity of theoutput gear 16. With the proportions shown in FIGS. 1-6, the output gear16 will come to a complete stop or dwell once in each revolution, sincethe pitch diameters of gears 14 and 16 are shown as being equal. If gear16 were twice as large as gear 14, it would experience two completestops per revolution. And if the gear 16 were replaced by a rack, theindex stroke of that rack would be the pitch circumference of the gear14. In all cases, whether the output member is a rotating gear as gear16 or a linearly moving rack, the output stroke is equal to the pitchcircumference of the gear 14. In the mechanism to be subsequentlydescribed, the output gear 16 has the same diameter as the gear 14 butthis is a convenience, not a necessity.

Furthermore, if the output member driven by the gear 14 is a linearlymoving rack, and if the centerline of shaft 10 passes through the pitchline of gear 14, then, as the link 6 becomes longer and longer, theoutput motion of the output rack member more closely approaches truecycloidal motion.

With the mechanism shown in FIG. 1, the output motion of gear 16 has thebroad characteristics of cycloidal motion, but distortions exist whichare caused by the short length of link 6 and the arcuate rather thanlinear path of shaft 22. To some degree, these distortions can becompensated for by the proper choice of gear ratio between input gear 2and driving gear 8 and the ratio of the length of link 6 to the centerdistance between input shaft 4 and output shaft 18.

In order to determine the exact quantitative kinematic characteristicsof the mechanism shown in FIG. 1, it is necessary to use numericalmethods for which a programmable calculator or computer is a greatconvenience, but not a necessity. Setting up classical equations ofmotion and then differentiating to find velocity and acceleration isexcessively laborious and time consuming. But numerical calculation forthe exact determination of the output shaft position for a series ofdiscrete positions of the input shaft can be accomplished usingstraightforward geometry and trigonometry. By making these calculationsat sufficiently small intervals, it becomes possible, by numericaldifferentiation, to obtain the velocity, and then by numericallydifferentiating a second time, to obtain the accelerations. Thesecalculations can be repeated as required for different values of thegeometrical parameters to closely approximate the conditions to bedescribed below.

Pure cycloidal motion displacement in unitized coordinates and usingradian angular notation is given by:

    S=1/2π(2πt-sin 2πt)                               (1)

where t is the input variable having a range of 0 to 1 for one cycle ofcycloidal motion, and S is the output displacement, also having a rangeof 0 to 1.

The velocity is obtained by differentiation, whereupon:

    V=1-cos 2πt                                             (2)

The acceleration is obtained by differentiating again, whereupon:

    A=2πsin2πt                                           (3)

The values for equations (1), (2), and (3) are graphically portrayed inFIGS. 7, 8 and 9. These are the curves representing the kinematicconditions for pure cycloidal motion. As noted above, the mechanism ofFIG. 1 can be made to generate approximate cycloidal motion of theoutput gear 6 for a constant angular velocity of the input gear 2 with areasonable degree of accuracy by a proper choice of geometric parametersdetermined by numerical calculation and successive approximation.

The specific characteristics of cycloidal motion which are important andrelevant to the mechanism of this invention are:

1. That the acceleration be substantially zero at the beginning and endof the index stroke as generated in the output gear 16. This creates arelatively long dwell which is useful for the shifting to beaccomplished.

2. That the peak velocity reached by the output gear 16 during its indexstroke by substantially double its average velocity over this stroke,and, further, that this peak velocity be reached at substantially themiddle of the output stroke.

It will be noted that at midstroke, S=1/2 and t=1/2, that theacceleration is zero and the instantaneous velocity has a peak value of2 which is twice the average velocity. If, at this point, as shown bythe conditions in FIG. 5, the eccentric gear 14 is disengaged from theoutput gear 16 by some suitable means, and an alternate appropriateconstant ratio driving means is engaged between the input shaft 4 andoutput gear 16, then the output gear 16 will continue to rotate at aconstant velocity having a peak value of 2.

In FIG. 10, an illustrative means of controlling the engagement of theeccentric gear 14 with the output gear 16 which permits selectiveengagement and disengagement of the gears is shown. A control link 24 ispivotally connected to the housing through a shaft 26. An arcuate slot28 which, for one position of the control link 24, has its center ofcurvature coincident with the center of the output gear 16, is formed inthe control link 24. The stub shaft 22 on gear 14 fits into and iscontrolled by the slot 28, the radial link 20 of FIG. 1 being removed.It can be seen that the arcuate slot 28 in the control link 24 canperform the same function, which is to keep the centers of the gears 14and 16 equidistant and their pitch lines in contact, if the center ofcurvature or arcuate slot 28 coincides with the centerline of the gear16. The control link 24 is actuated about the shaft 26 between twopositions by a cylinder 30 also mounted to the housing. These twopositions are controlled by stops 32 and 34; with the cylinder 30retracted, the link 24 is held against stop 32 and the slot 28 ispositioned to keep the gears 14 and 16 in engagement; with the cylinder30 extended, the link 24 is held against stop 34 and the slot 28 ispositioned to hold the gear 14 out of engagement with gear 16. Thismechanism of FIG. 10 is one illustrative means of controlling theengagement and disengagement of the eccentric gear 14 with the outputgear 16.

An illustrative constant ratio driving means between the input shaft 4and the output gear 16 is shown in FIG. 11. A secondary input gear 40 ismounted on the input shaft 4 adjacent the other input gear 2. A pivotedlink 42 is journalled on the input shaft 4 in suitable bearings; at itsother end, this link 42 is actuated by a cylinder 44 mounted to thehousing. An intermediate gear 46 and drive gear 48 are journalled in thelink 42, with the gear 46 in mesh with both gears 40 and 48. The link 42has two positions controlled by stops 50 and 52 on the housing. With thecylinder 44 extended, the position of link 42 is determined by stop 50and gear 48 is in pitch line contact with the output gear 16; with thecylinder 44 retracted, the position of link 42 is controlled by stop 52and the gear 48 is completely out of mesh with the output gear 16. Thepitch line velocity of gear 48 exactly matches the pitch line velocityof gear 16 when output gear 16 has reached its peak velocity as drivenby the cycloidal mechanism of FIGS. 1 and 10.

It can be seen, therefore, that if both cylinders 30 and 44 are extendedat the midpoint of the cycloidal drive mechanism cycle, the output gear16, having reached its peak velocity during 1/2 a revolution ofcycloidal acceleration by eccentric gear 14, is disengaged by gear 14and engaged by gear 48 which then continues to drive the output gear 16at that peak velocity.

This condition is shown by the velocity versus time diagram of FIG. 12.During the first half revolution of the output gear 16, which is reachedas t reaches 0.5, the velocity reaches a peak value of 2, as shown bypoint A on the velocity curve of FIG. 12. The displacement or movementis classically given as the area under the velocity curve and is shownas 60 in FIG. 12 and has a value of 0.5; it will be noted that theportion of the velocity curve of FIG. 12 for the value of t from 0 to0.5 is the same as the curve of FIG. 8 over that same range of t.

If, at the time when t reaches 0.5, as shown at A, the eccentric gear 14remains in mesh with the output gear 16, the velocity of that outputgear will follow the dashed line 62, as shown in FIG. 12, reaching 0 att=1, then building up to 2 again at t=1.5, as shown by point B. Duringthis interval, from point A to point B, the output gear 16 will havemoved through a displacement of one revolution, as shown by the area 64under the velocity curve 62 within this interval.

If, however, at the time when t reaches 0.5, the eccentric gear 14 isdisengaged from the output gear 16, as by extending the cylinder 30 ofthe illustrative mechanism of FIG. 10, and, if simultaneously, theoutput gear 16 is driven by a constant velocity mechanism as byextending the cylinder 44 of the illustrative mechanism of FIG. 11, thenthe velocity of the output gear 16 will be given by the line 66 of FIG.12. The total movement of the output gear, during the interval betweenpoints A and B (from t=0.5 to t=1.5, will be the area under the line 66between A and B or 2 revolutions, as shown by the sum of the areas 64and 68. If further, at t=1.5 (and at point B), the constant velocitymechanism of FIG. 11 is disengaged and the indexing mechanism of FIG. 10is re-engaged, the velocity of the output gear 16 again reaches a valueof 0 at t=2. The displacement of the output gear 16, during thisdeceleration is given by the area 70, which has a value of 1/2revolution.

With no shifts at points A or B, the output gear 16 velocity will followthe common curve from t=0 to t=0.5, then follows the curve 62 from t=0.5to t=1.5, and finally follows the common curve from t=1.5 to t=2. Thegear 16 will make two revolutions during the interval, as given by thesum of areas 60, 64, and 70. In essence, the gear 16 makes two simpleindex cycles.

However, if the shifts, described above, take place at A and B, thevelocity of the output gear 16 follows the common curve from t=0 to 0.5,then follows the curve (line) 66 from t=0.5 to t=1.5, and finallyfollows the common curve from t=1.5 to t=2. The gear 16 will make threerevolutions during the total interval, as given by the sum of the areas60, 64, 68, and 70. With shifting, the output gear 16 makes threerevolutions in the total interval t=0 to t=2, whereas, without shifting,the gear 16 makes only two revolutions in that same interval. Withshifting, the average velocity is 3/2 (S=3, t=2) while the peak velocityis 2. The ratio of the peak velocity to the average velocity is given by2/(3/2) or 4/3. Without shifting, the average velocity is 2/2 (S=2, t=2)or 1; and the ratio of the peak velocity is given by 2/1 or 2. It can beseen, therefore, that this technique of shifting greatly reduces theratio of peak velocity to average velocity for an indexing mechanism inwhich it is employed.

It is clear that the shifts which can be created by the mechanisms ofFIGS. 10 and 11 can only take place during that small range of time whenthe accelerating-decelerating mechanism of FIG. 10 is driving, or woulddrive, the output gear at maximum velocity, which, of course, is whenthe acceleration is at or near 0; this corresponds to a position forthis mechanism as schematically shown in FIG. 5. A shift at any othertime would create a velocity discontinuity of the output gear 16, whichimplies a theoretically infinite acceleration, and this is greatly to beavoided. That interval of time and position, during which the mechanismof FIG. 10 drives the output gear at substantially peak velocity(schematically shown in FIG. 5), will be subsequently referred to as the"CV window", where CV denotes constant velocity.

The mechanism of FIGS. 1 and 2 as modified by FIG. 10 will besubsequently referred to as the "AD mechanism" where AD denotesaccelerating-decelerating; and the mechanism of FIG. 11 will besubsequently referred to as the "CV mechanism" where CV denotes constantvelocity. The interval which corresponds to that time and position whenthe AD mechanism is temporarily in dwell, and the output gear 16 isstationary, will be referred to as the "dwell window". This correspondsto a position of the AD mechanism as shown in FIG. 10, and asschematically shown in FIG. 3. A time interval from a dwell window to aCV window or from a CV window to a dwell window will be subsequentlyreferred to as a module. (This also corresponds to the time or inputshaft angle required to rotate the eccentric gear 14 through one-halfrevolution.) It can be seen that such a module will have a time range of0.5 as from t=0 to t=0.5 or from t=1.5 to t=2, etc. It can further beseen that during any such module, the output gear 16 will rotate throughone half revolution when driven by the AD mechanism; and the output gear16 will rotate one full revolution when driven by the CV mechanism forone module.

A second velocity diagram based on a longer engagement of the CVmechanism is shown in FIG. 13. During the first module from t=0 tot=0.5, the output gear 16 is driven by the AD(accelerating-decelerating) mechanism. At the end of the module, theoutput gear reaches its peak velocity and is in a CV (constant velocity)window, having rotated one-half revolution during this interval and thepoint C is reached. If, during this CV window, the AD mechanism (FIG.10) is disengaged and the CV mechanism (FIG. 11) is engaged, the motionof the output gear is described by line 74 of FIG. 13. The output gear16 continues to rotate at constant velocity for four modules from t=0.5to t=2.5, and makes four revolutions during this time, and reachesanother CV window as shown at point D. At this point D, the CV mechanismis disengaged and the AD mechanism is re-engaged, and during the lastmodule of time from t=2.5 to t=3.0, the output gear is decelerated to adwell window making 1/2 revolution during this interval.

During the total interval from t=0 to t=3, which consists of sixmodules, the output gear 16 will make a total of five revolutions, whichis the sum of 1/2 revolution during the first (accelerating) module,four revolutions during the four modules at constant velocity betweenpoints C and D, and 1/2 revolution during the final decelerating module.The average velocity is, therefore, 5/3 (5 revolutions in 3 time units);and the ratio of peak velocity to average velocity is 2/(5/3)=1 1/5. Itcan be seen, therefore, that as the proportion of constant velocitymovement is increased, relative to a total cycle, the lower is the ratioof peak velocity to average velocity.

At the end of the first module when the first CV window was reached atpoint C, if no shift had taken place by engaging the CV mechanism anddisengaging the AD mechanism, the motion of the output gear 16 wouldhave been described by the dotted path 76, until the next CV windowappeared two modules later at point E, at which a shift could takeplace.

During the constant velocity movement of the output gear 16 along line74, this same CV window was passed at point E. Had the shift taken placeat E, rather than going on to point D, the same movement pattern wouldhave occurred as was described in connection with FIG. 12.

From the foregoing, it may be stated that CV windows appear at intervalsof two modules, and that during such a two module interval, the outputgear 16 will rotate through two revolutions while being driven by the CVmechanism, or, it will rotate through one revolution if, instead, it isdriven by the AD mechanism. If, during a CV window, the AD mechanism isdisengaged and the CV mechanism is engaged, this will be termed an"upshift"; similarly, if, during a CV window, the CV mechanism isdisengaged, and the AD mechanism is engaged, this will be termed a"downshift".

The motion of the output gear 16, represented by FIG. 12, may then besimply redescribed as follows. During the first time module, the outputgear 16 accelerates to maximum velocity and rotates through one-halfrevolution during this acceleration. It reaches a CV window and themechanisms upshift. The output gear 16 is then rotated at constantvelocity for an interval of two modules, while it makes two revolutions.It then reaches another CV window and the mechanisms downshift. Duringthe final module, the output gear 16 rotates through 1/2 revolutionwhile decelerating to a standstill at a dwell window.

The motion of the output gear 16 represented by FIG. 13 may also beredescribed as follows. During the first time module, the output gear 16accelerates to a maximum velocity and rotates one half revolutionthereby; it reaches a CV window and the mechanisms upshift. The outputgear 16 is then rotated at constant velocity for an interval of fourmodules, while it makes four revolutions. (It passed a CV window aftertwo modules but no shift took place.) After the aforesaid four modules,as the next CV window is reached, the mechanisms downshift. During thissixth and final module, the output gear rotates through 1/2 revolution,while decelerating to a standstill at a dwell window.

FIG. 12 illustrates two modules of constant velocity within a totalcycle of four modules; FIG. 13 illustrates four modules of constantvelocity within a total cycle of six modules. Similarly, it can be seenthat it is possible to construct a cycle of six modules of constantvelocity within a total cycle of eight modules resulting in a totaloutput of seven revolutions. Going still further, it is possible toconstruct a cycle of eight modules of constant velocity within a totalcycle of ten modules resulting in a total output of nine revolutions. Ina general sense, a cycle can be created having N modules, where N mustbe even and 2 or larger; then the number of modules of constant velocitywill be N-2 and the total output will be N-1 revolutions.

Since the width of a dwell window is fixed with respect to a givenmodule, the ratio of that dwell window with respect to the overall cyclewill decrease as the number of modules in a cycle increases. Inconventional applications for this invention, the input shaft 4 will bedriven by a suitable prime mover such as an electric motor, and standardgear reducer; and that prime mover, and the input shaft, will be stoppedat the end of each cycle, to restart at the beginning of the next cycle.Such a stopping and starting point for the input shaft mostadvantageously occurs during a dwell window, since at that time, theoutput shaft is accurately positioned and the accelerating anddecelerating characteristics are determined by the AD mechanism withminimal distortion due to the stopping or starting of the input shaft 4.Therefore, it is desirable to develop a means of extending the dwellperiod beyond that which is created by the natural dwell characteristicsof the AD mechanism.

In FIG. 14, one means of achieving such an expansion of the dwell, orstandstill time for the output gear 16, is shown. A holding lever 80 ismounted on a shaft 82 which is suitably journalled in the mechanismframe or housing. This holding lever 80 has mounted to it a rack segment84 which is formed to mesh with the teeth of the output gear 16. Theholding lever 80 is actuated through a small angle about the shaft 82 bya cylinder 86. With the cylinder 86 extended, as shown in FIG. 14, theteeth of the rack 84 mesh with the teeth of the output gear 16 andthereby effectively hold or lock it in position to prevent it fromrotating. With the cylinder 86 retracted, the holding lever 80 isrotated slightly counterclockwise on the shaft 82 to bring the lever 80into contact with a fixed stop 88 mounted on the frame. In this positionof the lever 80, the rack 84 is no longer in mesh with the teeth of theoutput gear 16, and the output gear 16 is therefore free to rotate asdriven by the AD mechanism or the CV mechanism. The entire mechanismshown in FIG. 14 will be referred to as the "holding" mechanism.

Referring to FIG. 12, it can be seen that at the end of the fourthmodule when t=2, the AD mechanism has brought the output gear 16 to atemporary standstill as shown by point F. At this time, it is possibleto engage the holding mechanism by extending cylinder 86, andsimultaneously disengaging the AD mechanism by extending cylinder 30(FIG. 10). The output gear 16 therefore remains stationary and lockedeven though the input shaft continues to rotate, driving both the ADmechanism and the CV mechanism, which are both disengaged from theoutput gear 16.

The AD mechanism may be re-engaged with the output gear 16 and theholding mechanism simultaneously disengaged at any time or point thatthe AD mechanism is in a dwell window position. These dwell windowpositions occur whenever the AD mechanism is in the position shown inFIGS. 1, 3 and 10; and, as can be seen from FIGS. 12 and 13 in thespacing of the 0 velocity points for unshifted movement, the timespacings of dwell windows are always two modules apart, just as the CVwindows are also always spaced two modules apart.

In the foregoing descriptions, the three separate mechanisms which driveor hold the output gear 16 are each shown as being actuated andcontrolled by separate independent cylinders. An alternate means foractuating and controlling all three mechanisms with a single cylinder isschematically shown in FIGS. 15 and 16. Where elements are functionallyidentical, but slightly modified by elimination of their actuatingcylinder connection, a suffix "a" is added to their identifying number.The control link 24a is mounted on the shaft 26; the arcuate slot 28controls the stub shaft 22 mounted concentrically on the eccentric gear14; the remainder of the gear train is the same as in FIG. 10 but isomitted for clarity. The control link 24a is not directly actuated by acylinder (as in FIG. 10), but is controlled by a cam follower roller 90mounted therein through bearings 92 (FIG. 16). This cam follower roller90 is engaged in a cam slot 94 in one arm 96 of a spider cam 97journalled on the output shaft 18.

The CV mechanism is similarly actuated and controlled. The link 42a isjournalled on the input shaft 4 and supports the drive gear 48; the geardrive train is again omitted for clarity and is the same as in FIG. 11.Whereas, in FIG. 11, the link 42 was actuated by a cylinder, the link42a in FIG. 15 is actuated and controlled by a cam follower roller 98mounted in the link 42a through bearings similar to those shown in FIG.16. This cam follower roller 98 is engaged in a cam slot 100 in anotherarm 101 of the spider cam 97.

The holding mechanism again consists of a link 80a mounted on a shaft 82journalled in the frame; the link 80a supports a rack section 84 and isactuated and controlled by a cam follower roller 102 engaged in a camslot 104 in the third arm 105 of the spider cam 97. The cam followerroller 102 is mounted in the link 80a through bearings comparable tothose shown in FIG. 16.

The spider cam 97 is actuated about its pivot axis on the output shaft18 by a three position cylinder 106 mounted in the frame. As shown inFIG. 15, the cylinder 106 and the spider cam 97 are in their middleposition as indicated by the reference line S2 on arm 101 of spider cam97 intersecting the cam follower roller 98. In this middle position, thecam slot 94 on spider arm 96 acting on cam follower roller 90 causes thecontrol link 24a to engage the eccentric gear 14 with the output gear16. In this same middle position for the spider cam 97, the cam slot 100on arm 101 acting on cam follower roller 98 causes the link 42a to keepthe gear 48 slightly out of engagement with the output gear 16;similarly, the cam slot 104 on spider arm 105 acting on the cam followerroller 102 positions the link 80a to keep the rack section 84 slightlyout of engagement with the output gear 16. In essence, the middleposition of the spider cam 97 engages the AD mechanism and disengagesthe CV mechanism and the holding mechanism.

With the cylinder 106 retracted, the spider cam 97 is rotated on theoutput shaft 18 through a small angle counterclockwise bringing thereference line S1 into intersection with the cam follower roller 98. Inthis full counterclockwise position of the spider cam 97, the cam slot94 in arm 96 acting on the cam follower roller 90 causes the eccentricgear 14 to be disengaged from the output gear 16; similarly, the camslot 100 in arm 101 acting on the cam follower roller 98 causes thedrive gear 48 to be disengaged from the output gear 16; and the cam slot104 in arm 105 acting on the cam follower roller 102 causes the racksection 84 to be engaged with the output gear 16 causing it to be heldin a locked position.

With the cylinder 106 fully extended, the spider cam 97 is rotated onthe output shaft 18 through a small angle in the clockwise directionbringing the reference line S3 into intersection with the cam followerroller 98. In this full clockwise position of the spider cam 97, the camslot 94 acting on the cam follower roller 90 causes the eccentric gear14 to be disengaged from the output gear 16; similarly, the cam slot 100acting on the cam follower roller 98 causes the drive gear 48 to beengaged with the output gear 16; and the cam slot 104 acting on the camfollower roller 102 causes the rack section 84 to be disengaged from theoutput gear 16.

In summary, with the spider cam 97 in its fully counterclockwiseposition S3, the holding mechanism is engaged, while the AD mechanismand CV mechanism are disengaged; with the spider cam 97 in its middleposition S2, the AD mechanism is engaged while the holding and CVmechanisms are disengaged; and with the spider cam 97 in its clockwiseposition S1, the CV mechanism is engaged, while the holding and ADmechanisms are disengaged. The use of a single spider cam 97 makes itpossible for one cylinder 106, to control all three mechanisms whichdrive or hold the output gear 16; the detail design of the cam slots 94,100, and 104 makes it possible to assure that the output gear 16 isalways engaged by at least one element that is used for its drive orholding which are the eccentric gear 14, the CV drive gear 48, or therack section 84. The use of the cam slots 94, 100, and 104 keeps thegear tooth separation loads mechanically close coupled, and they are notreflected back to the actuating cylinder 106 whenever the spider cam 97is in one of the three designated positions, S1, S2, or S3. Finally, theuse of the single spider cam 97 makes it possible, as will be shown, toprovide a simple automatically time or synchronized mechanical means toactuate the spider cam 97 in place of the cylinder 106 presently shown.

The mechanisms schematically illustrated in FIGS. 1, 2, 10, 11, 14, 15,and 16 were essentially schematic in nature to indicate the principlesof operation of this invention. The combined embodiment of thesesubassemblies, suitably refined and detailed, is shown in FIGS. 17-28.

The Acceleration-Deceleration (AD) Mechanism

Referring to FIGS. 17, 18, 19, 27 and 28, an input shaft 110 isjournalled in a housing 112 through bearings 114 and 116. The input gear118 for the AD mechanism is integrally formed on the input shaft 110.The tangential link is made up of two side plates 120 journalled on theinput shaft 110 through bearings 122; the side plates 120 are separatedby and bolted together through spacer blocks 124 (FIG. 19). Anintermediate gear 126 formed with integral shouldered stub shafts 128 isjournalled in the side plates 120 through bearings 130; thisintermediate gear 126 is also formed to mesh with the input gear 118. Adriving gear 132, also formed with integral shouldered stub shafts 134,is also journalled in the side plates 120 through bearings 136 (FIG.19); this driving gear 132 is formed to mesh with the intermediate gear126, and therefore is driven through the intermediate gear 126 from theinput gear 118. A cheekplate 138 is bolted to one side of the stub shaft134 of the driving gear 132; this cheekplate 138 in turn mounts theeccentric gear 140. It will be noted that the centerline of rotation ofthe driving gear 132 is very close to the pitch line of the eccentricgear 140. A cam follower roller 142 is concentrically mounted in theeccentric gear 140 through bearings 144; it will be used to control theposition of the eccentric gear as will be subsequently described. Theitems numbered 118-144 constitute the AD mechanism of this embodiment.

The Constant Velocity (CV) Mechanism

The structure of the CV mechanism of this embodiment is shown in FIGS.17, 20, 21 and 27. A secondary input gear 150 is also integrally formedon the input shaft 110. A link is formed of two side plates 152journalled on the input shaft 110 through bearings 154; the side plates152 are separated by and bolted together through spacer blocks 156 (FIG.20). An intermediate gear 158 formed with integral shouldered stubshafts 160 is journalled in the side plates 152 through bearings 162;this intermediate gear 158 is also formed to mesh with the secondaryinput gear 150. A driving gear 164 (FIG. 21), again formed with integralshouldered stub shafts 166, is also journalled in the side plates 152through bearings 168. This driving gear 164 is formed to mesh with theintermediate gear 158 and therefore is driven through the intermediategear 158 from the secondary input gear 150. A cam follower roller 170(FIG. 27) is mounted in the sideplates 152 through bearings 172; it isused to control the angular position of the side-plates 152, and thegear train mounted therein, about the axis of the input shaft 110, aswill be subsequently described. The items numbered 150-172 constitutethe CV mechanism of this embodiment. cl Output Shaft Assembly

The output shaft assembly is shown in FIGS. 17, 20 and 28 in thisembodiment. An output gear 174 is mounted on an output shaft 176journalled to the housing 112 through bearings 178 (FIG. 28). It will benoted that the housing 112 is formed with an external boss 180 and aninternal boss 182 to support the bearings 178. The output gear 174 isformed to mesh with the eccentric gear 140 and/or the driving gear 164.In this application, the output gear 174 has the same pitch diameter asthe eccentric gear 140.

The Holding Mechanism

The holding mechanism is shown in FIGS. 17, 20, 21 and 28. A holdinglink 184 is mounted on a shaft 186 suitably journalled in the housing112 (FIG. 20). A rack section 188 is mounted on the link 184 and isformed to mesh with the output gear 174 when the link 184 is positionedin its extended position. A cam follower roller 190 is journalled in thelink 184 through bearings 192; it will be used to control the positionof the holding link as will be subsequently described.

Control Link

Referring to FIGS. 17, 21, and 28, a control link 194 (FIG. 21) isformed into a boss 196 at its one end. This boss 196 is journalled to anauxiliary shaft 198 through bearings 200; the auxiliary shaft 198 isseparately journalled into the housing 112 (FIG. 17). An arcuate slot202 is formed into the control link 194, which is engaged by the camfollower roller 142 mounted in the eccentric gear 140 of the ADmechanism. In turn, a cam follower roller 204 is mounted in the controllink 194 through bearings 206; this cam follower roller 204 is used tocontrol the position of the control link 194 about the axis of theauxiliary shaft 198 as will subsequently be described. In the mostcounterclockwise position of the control link 194, the arcuate slot 202forms a true arc about the center of the output gear 174, and it is inthis position that the cam follower roller 142 holds the eccentric gear140 in engagement with the output gear 174.

The Spider Cam

Referring to FIGS. 17, 22, and 28, a spider cam 210 is journalled on theouter diameter of the internal boss 182 on the housing 112 throughbearings 212; the spider cam 210 is therefore able to be rotated aboutthe axis of the output shaft 176 since the boss 182 is concentrictherewith. The spider cam 210 is comprised of three arms: arm 214,associated with the control of the AD mechanism; arm 216, associatedwith the control of the CV mechanism; and arm 218, associated with thecontrol of the holding mechanism. A contoured cam slot 220 is milledinto the spider arm 214; it is engaged by the cam follower roller 204 onthe control link 194; this cam slot 220 controls the position of thecontrol link 194 and through it the engagement or disengagement of theeccentric gear 140 with the output gear 174.

A contoured cam slot 222 is milled into the spider arm 216; it isengaged by the cam follower roller 170 journalled in the side plates 152of the CV mechanism. This cam slot 22 therefore controls the engagementor disengagement of the driving gear 164 with the output gear 174. Fivereference lines, marked P1-P5, are positioned on the spider arm 216 inFIG. 22. These are used as a means of defining the angular position ofthe spider cam 210 about the axis of the output shaft. The spider cam210 is shown in the P2 position, i.e., the reference line P2 intersectsthe center of the cam follower roller 170. When the spider cam 210 isrotated counterclockwise through some small angle until the referenceline P1 intersects the center of the cam follower roller 170, theposition attained is defined as its P1 position. Similarly, throughslight clockwise rotations of the spider cam 210, the P3, P4, and P5positions can be reached, where in each case the position is defined asthat position in which the corresponding reference line intersects thecenterline of the cam follower roller 170.

A contoured cam slot 224 is milled into the spider arm 218; it isengaged by the cam follower roller 190 journalled in the holding link184. The cam slot 224 therefore controls the engagement or disengagementof the rack section 188 with the output gear 174.

As shown in FIG. 22, the three cam slots 220, 222 and 224 are configuredto create the conditions of engagement or disengagement of the threecontrolled mechanisms according to the following table.

                  TABLE I                                                         ______________________________________                                                Condition of Condition of Condition of                                Position of                                                                           AD Mechanism CV Mechanism Hold Mecha-                                 Spider Cam                                                                            to Output    to Output    nism to Out-                                210     Gear 174     Gear 174     put Gear 174                                ______________________________________                                        P1      Disengaged   Disengaged   Engaged                                     P2      Engaged      Disengaged   Engaged                                     P3      Engaged      Disengaged   Disengaged                                  P4      Engaged      Engaged      Disengaged                                  P5      Disengaged   Engaged      Disengaged                                  ______________________________________                                    

Actuation of the Spider Cam

It will be recalled that, in the schematic embodiment, as shown in FIG.15, the spider cam was actuated by a three position cylinder. In thisembodiment, the spider cam is directly mechanically actuated.

Referring to FIGS. 17, 22, 23 and 24, a drive arm 230 is mounted on theauxiliary shaft 198, which, as noted earlier, is journalled in thehousing 112; the outboard end of this drive arm 230 is formed into anopen parallel sided slot 232 whose sides are substantially parallel to aradial line through the center of the slot 232 which intersects the axisof the auxiliary shaft 198. A slide block 234 is closely fitted into theslot 232; this block 234 is journalled on a pin 236 (FIG. 23) mounted ontwo extensions 238 on the spider cam 210. It can be seen, therefore,that over a small range of angles, a movement imparted to the drive arm230 about its axis of rotation on the auxiliary shaft 198 is imparted tothe spider cam 210, moving about its own axis of rotation about the axisof the output shaft 176.

Referring also to FIGS. 25 and 26, a boss 240 is formed into the drivearm 230. A cam follower roller 242 is mounted into the boss 240 anddrive arm 230 through bearings 244 and 246. The boss 240 extends througha slot 248 in the housing 112; this permits the cam follower roller 242to engage a cam groove 250 in a master cam 252 mounted on the outside ofthe housing 112. The master cam 252 rotates on bearings 254 mounted on astub shaft 256 mounted on the housing 112 and held in axial position bya cover 258. The periphery of the master cam 252 is formed into gearteeth 260 which mesh with a pinion 262 at the outboard end of the inputshaft 110 (FIG. 27).

The groove 250 is configured to create the desired movements of thespider cam 210 and through it the interrelated movements of the ADmechanism, the CV mechanism and the holding mechanism. Because themaster cam 252 is mechanically driven by the input shaft 110, the propertiming or synchronization of the movements is assured if properlydesigned.

The illustrative cam groove 250 in master cam 252 is designed to createtwo modules of holding, one module of acceleration, two modules ofconstant velocity, and one module of deceleration. A series of referenceradial lines are superimposed on the cam groove 250 denoted M0 to M13.The cam 252 is shown in an angular position such that the cam followerroller 242 is at reference line M2 with respect to the cam slot; in thisposition, the eccentric gear 140 and the rack section 188 are bothsimultaneously in engagement with the output gear 174. The otherconditions of engagement at each of the other reference lines is shownin Table II below.

                  TABLE II                                                        ______________________________________                                                          Condition Condition                                                           of AD     of CV   Condition of                              Position of                                                                           Position of                                                                             Mechanism Mechanism                                                                             Hold Mecha-                               Master  Spider Cam                                                                              to Output to Output                                                                             nism to Out-                              Cam 252 210       Gear 174  Gear 174                                                                              put Gear 174                              ______________________________________                                        M0      P1        Disengaged                                                                              Disengaged                                                                            Engaged                                   M1      P1        Disengaged                                                                              Disengaged                                                                            Engaged                                   M2      P2        Engaged   Disengaged                                                                            Engaged                                   M3      P3        Engaged   Disengaged                                                                            Disengaged                                M4      P3        Engaged   Disengaged                                                                            Disengaged                                M5      P4        Engaged   Engaged Disengaged                                M6      P5        Disengaged                                                                              Engaged Disengaged                                M7      P5        Disengaged                                                                              Engaged Disengaged                                M8      P5        Disengaged                                                                              Engaged Disengaged                                M9      P4        Engaged   Engaged Disengaged                                 M10    P3        Engaged   Disengaged                                                                            Disengaged                                 M11    P3        Engaged   Disengaged                                                                            Disengaged                                 M12    P2        Engaged   Disengaged                                                                            Engaged                                    M13    P1        Disengaged                                                                              Disengaged                                                                            Engaged                                   ______________________________________                                    

It will be noted from Table II that at the positions of the master cam252, M2, M5, M9, and M12 two mechanisms are simultaneously engaged withthe output gear 174. This is a momentary condition only, for as onemechanism reaches full engagement with the output gear 174, the othermechanism begins to disengage. Since the pressure angle of the gearteeth creates a natural taper, this is a permissible technique to use;furthermore, with this momentary simultaneous engagement of twomechanisms with the output gear 174, it is impossible for the outputgear to be even momentarily uncontrolled.

A composite timing diagram for the system, corresponding to the controlfunction of the cam groove 250, is shown in FIG. 29. The upper curverepresents the velocity of the output gear 174 and is analogous to FIG.12 except that two modules of holding have been added. It can be seenthat an entire cycle, represented by one revolution of the master cam252, consists of six modules, which are arbitrarily numbered from thecenter of the holding range. Referring to the velocity graph of FIG. 29,it can be seen, that during the first module, the output gear 174 isstationary; during the second module, it accelerates to maximumvelocity; during the third and fourth module, the output gear 174operates at constant velocity; during the fifth module, it deceleratesback to a standstill; and during the sixth module, it remainsstationary. On this same velocity graph is superimposed a dotted linewhich represents the hypothetical velocity of the output gear 174, ifthe eccentric gear 140 remained engaged with the output gear 174, andthe driving gear 164 and rack section 188 remained engaged. It will benoted that the reference lines M0-M13 have been superimposed on FIG. 29and correspond in time relationship with the lines so marked on FIG. 25.Reference lines M0, M2, M5, M7, M9 and M12 coincide with the linesseparating the modules.

Directly below the velocity diagram are added three schematic timeposition diagrams for the three mechanisms which selectively engage anddisengage the output gear 174. The upper diagram shown by line 270indicates the engaged and disengaged status of the holding mechanismduring a cycle. Similarly, the diagrammatic line 272 indicates theengaged and disengaged status of the AD mechanism during a cycle; and,finally, the bottom line 274 indicates the engaged and disengaged statusof the CV mechanism during a cycle. This cycle of six modules willrepeat endlessly as long as the prime mover which drives the input shaftrotates in a given direction. In situations in which unidirectionaloperation is desired, together with a longer dwell than is provided bythe two modules of hold, the prime mover may be stopped at any timeduring the hold modules. Since the output gear 174 will already bestationary as a function of the overall mechanism characteristics, sucha stopping position of the prime mover and the input shaft is verynon-critical.

In reversing applications, the prime mover and input shaft must stop atthe end of each cycle, but the stopping point is again verynon-critical. After an index in the one direction as shown by FIG. 29,the prime mover and input shaft can stop at any point after module 5, asdefined by reference line M12; the amount that the system moves intomodule 6, or even into module 1 is of no consequence insofar as theposition of the output gear is concerned. It is clear that the mechanismcan operate equally well in either direction; therefore, to reverse themechanism, the prime mover and input shaft are rotated in the reversedirection and the overall mechanism executes the functions of modules 5,4, 3, and 2 in that order, bringing the output shaft 176 to a stop asmodule 1 is reached. Again, the amount that the system moves into module1, or even into module 6, is of no consequence insofar as the positionof the output gear is concerned. However, the amount the system movesinto the hold modules, 1 or 6, at the end of each reversing index is ofconsequence insofar as the time required for a given index is concerned,since the time required to retrace the distance moved into a given holdmodule is added to the time required for the next reversing cycle.Accordingly, it is desirable to move into the hold modules, 1 or 6, atthe ends of the actual index movement (modules 2, 3, 4 and 5) as littleas possible to reduce the overall cycle times.

The cam 252, with its cam groove 250, is illustrative only, and causesthe embodiment of FIGS. 17-28 to execute the movement sequence of FIG.29, which is three revolutions of the output shaft made of 1/2revolution of acceleration, 2 revolutions of constant velocity, and 1/2revolution of deceleration. This is true for operation in eitherdirection.

Other program sequences can be designed into the master cam 252,consistent with the simple rules to be reiterated. The gear ratiobetween the input shaft pinion 262 and the gear 260 on the periphery ofthe master cam 252 determines the total number of modules for an overallcycle; this is shown as 6 modules in FIG. 25. By changing this gearratio, it is possible to design and utilize a master cam which provides8, 10, or more modules per cycle.

The design provisions or rules in designing a master cam can be statedas follows:

1. A module consists of an interval in terms of time or input shaftangle from a dwell window to a CV window, as earlier defined, or viceversa. Such a module also comprises the time or input shaft anglerequired to rotate the eccentric gear 140 through substantially 1/2revolution.

2. The acceleration of the output gear 174 from a dwell to a maximumvelocity condition requires 1 module, during which it rotates through1/2 revolution, if the eccentric gear 140 and output gear 174 are thesame diameter.

3. The deceleration of the output gear 174 from a maximum velocitycondition to a dwell condition also requires one module, during which italso rotates through 1/2 revolution, if the eccentric gear 140 and theoutput gear 174 are the same diameter.

4. In a complete cycle, there must be one deceleration module for everyacceleration module to prevent discontinuities in output gear velocity.Therefore, the sum of acceleration modules and deceleration modules mustbe even (2, 4, 6, etc.).

5. The positions of CV windows occur at like angular positions of theeccentric gear 140, which positions are one or more revolutions apart.Since a module is substantially 1/2 revolution of the eccentric gear140, the CV windows are always spaced 2 modules apart; therefore, thenumber of CV modules must also always be even.

6. The positions of the dwell windows also occur at like angularpositions of the eccentric gear 140, which positions are also one ormore revolutions apart; therefore, the number of dwell or hold modulesmust also always be even.

7. Since the number of CV modules and dwell modules must each always beeven, and since the sum of the acceleration and deceleration modulesmust be even, it follows that the total number of modules controlled bya master cam must also always be even.

8. Finally, it is clear, that an acceleration module must always be usedin transition from a dwell module to a constant velocity module, and adeceleration module must be used in transition from a constant velocitymodule to a dwell module, bearing in mind that when the mechanism isreversed, an acceleration module becomes a deceleration module and viceversa.

Within the framework of the above stated rules, it is possible to designa master cam to create any predetermined pattern of motion, which is, ofcourse, repeated during each revolution of said cam. Or, if the primemover and input shaft are reversed, the cam also turns in the oppositedirection, reversing the pattern. For an arrangement such as in FIG. 29,where the pattern of movement is symmetrical, a reversal maintains thesame pattern.

It can be seen that as the number of modules in a total cycle isincreased, the gear ratio between the pinion 262 and gear 260 on themaster cam must be increased. The cam rise ramp angles of the cam groove250 also will increase as the number of modules that correspond to onerevolution of the cam is increased, since the radial rise of the camgroove is compressed into a smaller angular distance on the cam. Thenumber of modules which correspond to one revolution of the master camis therefore limited by the maximum workable cam groove 250 rise angleswhich must follow good engineering practice. There are two ways in whichthe number of modules in a given cycle may be increased. One is to makethe master cam 252 larger, thereby increasing the length of the camgroove 250. The second is to replace the constant velocity drive systembetween the input shaft 110 and master cam 252, as represented by thepinion 262 and gear 260, with an intermittent drive system. Such anintermittent drive system could consist of a connection as simple orconventional as the well known Geneva mechanism with the input shaft 110as the driving member and the master cam as the driven member, eitherdirectly, or through an intermediate Geneva output (slotted) member. Anyof the standard cam index mechanisms could also advantageously beinterposed between the input shaft 110 and the master cam 252.

The introduction of an intermittent motion mechanism, such as the Genevaor cam mechanisms, especially those having a long dwell, would cause themaster cam 252 to move forward in discrete imcrements separated bylarger periods of dwell. For example, a conventional Geneva mechanismhaving a 90° output movement has a cycle in which the output member isstationary for 270° of input movement, then moves through its outputangle of 90° during 90° of input movement; in other words, 3/4 dwelltime to 1/4 movement time. By properly phasing such an intermittentmotion mechanism to create an intermittent motion of the master cam 252from the input shaft 110, it becomes possible to reduce the rise anglesin the cam groove 250 as compared to the pinion and gear drive.

In the foregoing description of the mechanisms, it was shown that theacceleration of the output gear occurred during one half revolution; andthat the deceleration also occurred during one half revolution thereof.This condition was created by having the eccentric gear the samediameter as the output gear, such that the fullacceleration-deceleration of the output gear, without shifts, occursduring one revolution of that output gear.

However, the techniques described above can also be applied to systemsin which the eccentric gear and the output gear are not of identicalsize. As an example, let the eccentric gear be one half the diameter ofthe output gear. Then in a non-switched operation, the output gear wouldmove through a complete acceleration-deceleration cycle from dwell todwell in one half revolution; this corresponds to one full revolution ofthe eccentric gear, as is always the case. Presuming that theacceleration-deceleration profile has been made sufficiently close tothat of a pure cycloid by appropriate control of the geometricparameters, it can be seen that the output gear moves from a dwellwindow to peak velocity at a CV window in one quarter revolutionthereof. The time required to do this is again defined as one module;and the time required for the output gear to decelerate from peakvelocity at a CV window to a dwell window will also be one module,during which interval it rotates through 1/4 revolution. Further, sincefor a cycloid, the peak velocity is double the average velocity, thedistance moved by the output gear in one module, if it moves at aconstant speed which is the same as the cycloidal peak speed, will betwice the distance it would move in an accelerating or deceleratingmodule. Therefore, in a constant velocity module, it would move throughone half revolution, which is twice the one quarter revolution movedduring either the accelerating or decelerating module. The CV windowswould still be spaced two modules apart as earlier noted. A four modulecycle, analogous to FIG. 12, would exhibit the followingcharacteristics. During the first module, the output gear accelerates topeak velocity and reaches the CV window after rotating one quarterrevolution; and an upshift occurs; during the next two modules, theoutput gear rotates at constant velocity and rotates through onecomplete revolution to reach the next CV window where a downshiftoccurs. During the fourth and final module, the output gear deceleratesfrom the CV window to a dwell window while rotating through one quarterrevolution. The total rotation of the output gear during all fourmodules of the cycle is therefore 11/2 revolutions.

In the general case where the ratio of the eccentric gear diameter tothe output gear diameter is given by R, the number of revolutions madeby the output gear during an acceleration-deceleration cycle withoutshifting or constant velocity is R revolutions. During an acceleratingmodule from a dwell window to a CV window, or during a deceleratingmodule from a CV window to a dwell window, the number of revolutionsmade by the output gear is R/2 revolutions. During a constant velocitymodule, the number of revolutions made by the output gear is 2×R/2 or Rrevolutions. For a total cycle of N modules, exclusive of hold modules,it will be recalled that N-2 modules are used for constant velocity.Therefore, the total number of revolutions, M, made by the output gearof a system having a ratio of R and operating on an N module cycle isthe sum of the following:

R/2 revolutions during acceleration

R(N-2) revolutions during constant velocity

R/2 revolutions during deceleration

Therefore,

M=R/2+R(N-2)+R/2

M=R+R(N-2)

M=R(N-1)

It will be recalled that N must always be an even number and with thislimitation, when R is 1, as in the specific mechanisms described, M canbe 1, 3, 5, 7, etc. Therefore, if it is desired that M be some evennumber such as 2, then

2=R(N-1)

For a 4 module cycle, N=4, whereupon R=2/3; for a 6 module cycle, N=6,and R=2/5. In a general sense, by being able to vary R, it becomespossible to design an overall system having an even number of modulesand any reasonable number of output revolutions, integral or rational.

In the invention described above, the AD mechanism utilized the systemdisclosed in my U.S. Pat. No. 3,789,676. This system does not includethe addition of higher harmonic components. An accelerating-deceleratingmechanism which does incorporate the addition of higher harmoniccomponents is disclosed in my U.S. Pat. No. 4,075,911. The relevantembodiments of this U.S. Pat. No. 4,075,911 can also be utilized in thispresent invention. It will be noted from this existing patent that ahigher harmonic component can be added to the kinematic characteristicsof the AD (accelerating-decelerating) mechanism by introducing aneccentricity between the axis of the input shaft and the axis of theinput drive gear which latter axis is also the pivot axis of the linkassociated with the AD mechanism. It is comparatively simple to add thiseccentricity to this present invention as is shown in FIG. 30 which isto be compared to FIG. 19.

Referring to FIG. 30, a revised two-piece input shaft 110a and 110b (forassembly purposes) is mounted as before in suitable bearings in thesupport housing and rotates on an axis A₀. The input gear 118 iscentered on an eccentric axis A₁ displaced some small distance from theaxis A₀. The side plates 120 are journalled on the input shaft 110a,110b through bearings 122 which are concentric with the eccentric axisA₁. The remainder of the gear train, bearings, and other components ofthe AD mechanism are the same as described in connection with FIG. 19,except that the cheekplate 138a is slightly altered to provide for acompensating revised eccentricity between the driving gear 132 and theeccentric gear 140. The remainder of the input shaft 110a, 110b isunaltered from the configuration described in connection with FIGS. 19and 27. Specifically, the secondary input gear 150 remains concentricwith the axis A₀ of the input shaft 110a, 110b as do the seats for thebearings 154 (FIG. 21).

As will be noted from the kinematic explanations in my U.S. Pat. No.4,075,911, the addition of a higher harmonic component creates a largedegree of kinematic design flexibility. Specifically, when this featureis incorporated into this present invention, it becomes possible todesign a kinematic behavior for the AD mechanism such that the inherentnatural dwell is significantly improved and, simultaneously, thevelocity can be made to remain more nearly constant over a longer rangein the midstroke region. Stated another way, both the dwell window andCV window can be enlarged. This makes the shift points less critical andpermits more time or input shaft angle for shifting. This in turnpermits lower ramp angles on both the spider cam and master cam.

The specific camming arrangement shown in this invention employs a threearmed spider cam which directly controls the positions of the ADmechanism, the CV mechanism, and the holding mechanism; and this spidercam in turn is controlled by a master cam. In other words, one camdrives another. It is also possible to devise a camming arrangement inwhich a suitable camshaft, driven by the input shaft at some appropriateratio, carries three separate cams, one of which controls the positionof the AD mechanism, another controls the position of the CV mechanism,and the third controls the position of the holding mechanism, eachcontrolling its mechanism either directly or through some conventionallinkage.

The incorporation of a holding mechanism which comprises elements184-192 is useful in creating a far longer dwell of the output memberthan is attainable without it. However, in some few applications,generally those which operate at relatively low speed, the natural dwellof the accelerating-decelerating mechanism is sufficient and the holdingmechanism can be deleted. In such designs, it is further possible todelete the arm 218 with its cam groove 224 on the spider cam 210 formanufacturing economies; the positions P1 and P2 (FIG. 22) for thespider cam 210 would be deleted and it would operate only betweenpositions P3, P4, and P5, and this would reflect into the design of themaster cam 252. With these simplifications, the mechanism could onlyoperate in the accelerating-decelerating mode or in the constantvelocity mode and the only dwell would be the natural dwell of theaccelerating-decelerating mechanism.

In the various embodiments shown herein, the driving connection betweenthe input gear to the driving gear, as from input gear 118 to drivinggear 132, was shown as being made through an intermediate gear, as gear126. It can be seen that the intermediate gear may be replaced by adriving connection employing sprockets and chains, or, for lightlyloaded applications, even cog-type belts and pulleys. Such connectionsare shown in my existing U.S. Pat. Nos. 3,789,676 and 4,075,911.Similarly, the intermediate gear of the constant velocity mechanism,such as gear 158, may be replaced by such other driving connections.

I claim:
 1. A reversible rotary indexing mechanism capable of generatinglarge indexing angles, including those exceeding one revolution, whichcomprises:(a) a frame, (b) output means mounted for rotation in saidframe, (c) input means mounted for rotation in said frame, (d)accelerating-decelerating drive means operatively associated with saidinput means and selectively engageable with said output means and, whenengaged with said output means and driven by a constant predeterminedvelocity of said input means, drives said output means at a cyclicallyvarying velocity accelerating from a substantially zero velocity to apredetermined maximum velocity and then decelerating to a substantiallyzero velocity in a repetitive cycle, (e) constant velocity drive meansoperatively associated with said input means and selectively engageablewith said output means, and, when engaged with said output means anddriven by said constant predetermined velocity of said input means,drives said output means at a constant velocity substantially equal tosaid predetermined maximum velocity, and (f) shifting means operativelyassociated with said accelerating-decelerating means and with saidconstant velocity means, and adapted to disengage saidaccelerating-decelerating means from said output means at its saidpredetermined maximum velocity and substantially simultaneously toengage said constant velocity means with said output means, and furtheradapted to subsequently disengage said constant velocity means from saidoutput means and substantially simultaneously to re-engage saidaccelerating-decelerating means with said output means at a position inthe cycle of said accelerating-decelerating means when it drives saidoutput means at said predetermined maximum velocity.
 2. A mechanism asin claim 1 which further comprises holding drive means mounted in saidframe and selectively engageable with said output means, and, whenengaged with said output means, holds said output means from movement,and said shifting means is further operatively associated with saidholding drive means and adapted to disengage saidaccelerating-decelerating means from said output means at its said zerovelocity and substantially simultaneously to engage said holding drivemeans with said output means, and said shifting means is further adaptedto subsequently disengage said holding drive means from said outputmeans and substantially simultaneously to reengage saidaccelerating-decelerating means with said output means at a position inthe cycle of said accelerating-decelerating drive means when it drivessaid output means at said zero velocity.
 3. A mechanism as in claim 1 inwhich said accelerating-decelerating drive means imparts to the outputmeans, when selectively engaged therewith, a cyclically and smoothlyvarying velocity periodically reaching substantially zero velocity andin which the average velocity during any one cycle is substantiallyone-half the maximum velocity reached during said one cycle.
 4. Amechanism as in claim 3 in which said accelerating-decelerating drivemeans imparts to the output means, when selectively engaged therewith, amotion substantially identical with the motion commonly referred to ascycloidal motion.
 5. A mechanism as in claim 1 in which saidaccelerating-decelerating drive means comprises:(a) a first drive memberconcentrically mounted on said input means and rotating about a firstaxis, (b) support means mounted for oscillation about said first axis,(c) a second drive member mounted for rotation in said support means androtating about a second axis displaced from said first axis, (d) meansconnecting for rotation said first drive member and said second drivemember, (e) an eccentric member concentric about a third axis displacedfrom said second axis and mounted on said second drive member andadapted to drive said output means, and (f) guide means controlling thepath of said third axis of said eccentric member selectively movablebetween two positions: a first position in which said eccentric memberis held out of engagement with said output means, and a second positionin which said eccentric member is held in engagement with said outputmeans as said third axis on said eccentric member oscillates along anarcuate path substantially equidistant from the axis of said outputmeans.
 6. A mechanism as in claim 1 in which said output means comprisesan output gear and in which said accelerating-decelerating drive meanscomprises:(a) a first drive member concentrically mounted on said inputmeans and rotating about a first axis, (b) support means mounted foroscillation about said first axis, (c) a second drive member mounted forrotation in said support means and rotating about a second axisdisplaced from said first axis, (d) means connecting for rotation saidfirst drive member and said second drive member, (e) an eccentric gearconcentric about a third axis displaced from said second axis andmounted on said second drive member and adapted to mesh with said outputgear, and (f) guide means controlling the path of said third axis ofsaid eccentric gear selectively movable between two positions: a firstposition in which said eccentric gear is held out of engagement withsaid output gear, and a second position in which said eccentric gear isheld in engagement with said output gear as said third axis on saideccentric gear oscillates along an arcuate path substantiallyequidistant from the axis of said output gear.
 7. A mechanism as inclaim 6 in which said eccentric gear has mounted thereon a stub shaftconcentric about said third axis, and said guide means comprises a guidemember pivotally supported from said frame and containing an arcuateslot adapted to control the path of said stub shaft and said guidemember is selectively movable between two positions: a first position inwhich said arcuate slot holds said eccentric gear out of engagement withsaid output gear, and a second position in which the center of curvatureof said arcuate slot is substantially coincident with the center of saidoutput gear and said eccentric gear is held in engagement with saidoutput gear as said stub shaft oscillates in said arcuate slot.
 8. Amechanism as in claim 7 in which the radius of said arcuate slot issubstantially equal to the sum of the pitch radius of the eccentric gearand the pitch radius of the output gear.
 9. A mechanism as in claim 6 inwhich said first drive member comprises a first gear and in which saidsecond drive member comprises a second gear and in which said meansconnecting for rotation comprises an intermediate gear interposedbetween said first gear and said second gear.
 10. A mechanism as inclaim 1 in which said input means rotates about a first axis and saidaccelerating-decelerating means comprises:(a) a first drive memberconcentric about a second axis and eccentrically mounted on said inputmeans with said second axis displaced from said first axis, (b) supportmeans mounted for oscillation about said second axis, (c) a second drivemember mounted for rotation in said support means and rotating about athird axis displaced from said second axis, (d) means connecting forrotation said first drive member and said second drive member, wherebysaid first drive member rotates an integral number of revolutions foreach revolution of said second drive member, (e) an eccentric memberconcentric about a fourth axis displaced from said third axis andmounted on said second drive member and adapted to drive said outputmeans, and (f) guide means controlling the path of said fourth axis ofsaid eccentric member selectively movable between two positions: a firstposition in which said eccentric member is held out of engagement withsaid output means, and a second position in which said eccentric memberis held in engagement with said output means as said fourth axis on saideccentric member oscillates along an arcuate path substantiallyequidistant from the axis of said output means.
 11. A mechanism as inclaim 1 in which said input means rotates about a first axis and inwhich said output means comprises an output gear and in which saidaccelerating-decelerating drive means comprises:(a) a first drive memberconcentric about a second axis and eccentrically mounted on said inputmeans with said second axis displaced from said first axis, (b) supportmeans mounted for oscillation about said second axis, (c) a second drivemember mounted for rotation in said support means and rotating about athird axis displaced from said second axis, (d) means connecting forrotation said first drive member and said second drive member, wherebysaid first drive member rotates an integral number of revolutions foreach revolution of said second drive member, (e) an eccentric gearconcentric about a fourth axis displaced from said third axis andmounted on said second drive member and adapted to mesh with said outputgear, and (f) guide means controlling the path of said fourth axis ofsaid eccentric gear selectively movable between two positions: a firstposition in which said eccentric gear is held out of engagement withsaid output gear, and a second position in which said eccentric gear isheld in engagement with said output gear as said fourth axis on saideccentric gear oscillates along an arcuate path substantiallyequidistant from the axis of said output gear.
 12. A mechanism as inclaim 11 in which said eccentric gear has mounted thereon a stub shaftconcentric about said fourth axis, and said guide means comprises aguide member pivotally supported from said frame and containing anarcuate slot adapted to control the path of said stub shaft and saidguide member is selectively movable between two positions: a firstposition in which said arcuate slot holds said eccentric gear out ofengagement with said output gear, and a second position in which thecenter of curvature of said arcuate slot is substantially coincidentwith the center of said output gear and said eccentric gear is held inengagement with said output gear as said stub shaft oscillates in saidarcuate slot.
 13. A mechanism as in claim 11 in which the radius of saidarcuate slot is substantially equal to the sum of the pitch radius ofthe eccentric gear and the pitch radius of the output gear.
 14. Amechanism as in claim 11 in which said first drive member comprises afirst gear and in which said second drive member comprises a second gearand in which said means connecting for rotation comprises anintermediate gear interposed between said first gear and said secondgear.
 15. A mechanism as in claim 1 in which said constant velocitydrive means comprises:(a) a first drive member concentrically mounted onsaid input means and rotating about a first axis, (b) support meansmounted for movement about said first axis, (c) a second drive membermounted for rotation in said support means and rotating about a secondaxis displaced from said first axis and adapted to drive said outputmeans, and (d) means connecting for rotation said first drive member andsaid second drive member.
 16. A mechanism as in claim 1 in which saidoutput means comprises an output gear and in which said constantvelocity drive means comprises:(a) a first gear concentrically mountedon said input means and rotating about a first axis, (b) support meansmounted for movement about said first axis, (c) a second gear mountedfor rotation in said support means and rotating about a second axis andadapted to drive said output gear, and (d) means connecting for rotationsaid first gear and said second gear.
 17. A mechanism as in claim 16 inwhich said means connecting for rotation comprises an intermediate gearmounted for rotation on said support means and interposed between saidfirst gear and said second gear.
 18. A mechanism as in claim 1 in whichsaid shifting means comprises: cam means operatively associated withsaid accelerating-decelerating drive means and with said constantvelocity drive means and adapted to selectively engage said drive meanswith said output means.
 19. A mechanism as in claim 18 in which said cammeans is actuated by cylinder means.
 20. A mechanism as in claim 18 inwhich said cam means is driven by said input means.
 21. A mechanism asin claim 18 in which said cam means comprises:(a) a first cam memberpivotally mounted to rotate about the axis of said output means andhaving a first cam arm operatively associated with saidaccelerating-decelerating drive means and a second cam arm operativelyassociated with said constant velocity drive means, and (b) a second cammember mounted for rotation on said frame and driven by said input meansand operatively associated with said first cam member.
 22. A mechanismas in claim 2 in which said shifting means comprises cam meansoperatively associated with said accelerating-decelerating drive means,and with said constant velocity drive means and with said holding drivemeans and adapted to selectively engage said drive means with saidoutput means.
 23. A mechanism as in claim 22 in which said cam means isactuated by cylinder means.
 24. A mechanism as in claim 22 in which saidcam means is driven by said input means.
 25. A mechanism as in claim 22in which said cam means comprises:(a) a first cam member pivotallymounted to rotate about the axis of said output means and comprising:1.a first cam arm operatively associated with saidaccelerating-decelerating drive means,
 2. a second cam arm operativelyassociated with said constant velocity drive means,
 3. a third cam armoperatively associated with said holding drive means, and (b) a secondcam member mounted for rotation on said frame and driven by said inputmeans and operatively associated with said first cam member.